The folks at Mozilla have released new versions of their Firefox Web browser, version 3.6.13, and their Thunderbird E-mail client, version 3.1.7, for all platforms: Windows, Mac OS X, and Linux.
The new version of Thunderbird fixes three security flaws, all rated Critical. It also incorporates improvements in the handling of large mail folders, and in the handling of local copies of IMAP mail. See the Release Notes for more information.
You can get the new version of either package by using the built-in update mechanism (Help / Check for Updates), or you can get complete installation packages for all platforms, in a variety of languages, from the Firefox download page, or the Thunderbird download page.